I was reading a post by Harry Murphey commenting on a block to make the Mast Caddy fit better on the rear cross bar. I have this issue, when clamping down on the crossbar the blocks get very crooked and I dont trust it to stay on when trailering so I wrap a bungee cord around the base and connect to my tramp lacing.

Since I dont have the block they came out with is there a better solution to keeping the caddy in place. Though I would say I have made a couple of 7+ hour trips with no issues. Just not sure I trust it.

I just went out and measured the "block" that was supplied w/ my mast caddies ... (I have two, one for my H18 and one for my P19MX ...) The material used for the block is 9/16" thick X 3" long X 1 3/8 wide. The material is black plastic ... but I don't think the material matters all that much ... you could use a piece of wood, plywood, plastic, etc ....

Now so I wouldn't loose the block, I drilled a small hole in the block and another small hole in the bottom "crossbar clamping" section and using a 1' long piece of batten string as a "safety line" tied the "block" to the bottom section so that I wouldn't loose the block.

For the H18 the "block is installed horizontally ... for my P19MX w/ it's much thicker rear crossbar you place the "block" on edge ..... then just tighten down on the knob .....

I have been thinking of drilling a small hole in the threaded bolt and installing a cotter-pin or clivis ring so I can never loose the knob .... but it has never loosened up .... so that maybe "overkill" ....

It sounds like you do the samething as me w/ a bungie cord wrapped around the mast caddy and pulled forward, attaching to the center lacings. My 3/8" bungie is long enough that it attaches up near my forward crossbeam ....

What is this block supposed to do? I threw mine away thinking it was something the previous owner had jury rigged.... The block seemed to prevent the clamp from squeezing down tight on the cross bar, I think it works better without it.

Thanks for the pics. Here are mine. I reversed the clamp brackets - this made mine stay on better. But it looks like you have some type of block between your clamping blocks. This must be what Harry is talking about. You can see how uneven my blocks are without it.

The block does keep the clamping surfaces even. I had one of these on a 16 and it was the best caddie I ever had, should have never sold it with the boat. I never used it on an 18 but with even clamping it should work great. Just screw it down tight every time, i also used a backup bungee still do with what ever I use to hold a mast.